Mathematics - Bachelor's degreehttp://hdl.handle.net/1721.1/7681
Mon, 16 Oct 2017 22:14:38 GMT2017-10-16T22:14:38ZTesting models of ultra-fast India-Asia convergence : new paleomagnetic results from Ladakh, Western Himalayahttp://hdl.handle.net/1721.1/90648
Testing models of ultra-fast India-Asia convergence : new paleomagnetic results from Ladakh, Western Himalaya
Bailey, Elizabeth A
Rapid India-Asia convergence has led to a major continental collision and formation of the Himalayas, the highest mountain range on Earth. Knowledge of the paleolatitude of the Kohistan-Ladakh Arc (KLA), an intermediate tectonic unit currently situated between the converging Indian and Eurasian continents in Western Himalaya, would constrain the tectonic history and dynamics of Himalayan orogenesis. We present new paleomagnetic data from the Khardung volcanic rocks of the Shyok-Nubra valley region of Ladakh, western Himalaya. Samples from all four sites (KP1-KP4) display high-temperature components indicating a roughly equatorial paleolatitude, with the average of site mean directions implying a paleolatitude of 5'N. We interpret results of a positive baked contact test at one site (KP3) to imply that the high-temperature components in the distal volcanic bedrock predate bedding tilt and dike formation. Previous studies of the Khardung unit (Bhutani 2009, Dunlap 2002) have measured 40Ar-39Ar and U-Pb dates of -52-67 Ma. Assuming these ages apply to our samples, our results support the two-stage collision model of Jagoutz and Royden (in prep), which indicates an approximately equatorial India-KLA collision at 50 Ma.
Thesis: S.B., Massachusetts Institute of Technology, Department of Mathematics, 2014.; Author received an S.B. from the Department of Mathematics, but her thesis was submitted to the Department of Earth, Atmospheric and Planetary Sciences for the degree of S.B. Cataloged from PDF version of thesis.; Includes bibliographical references (pages 29-32).
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/1721.1/906482014-01-01T00:00:00ZPhoenix : an interactive hierarchical topological floorplanning placerhttp://hdl.handle.net/1721.1/77677
Phoenix : an interactive hierarchical topological floorplanning placer
Chow, Chee-Seng
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (B.S.)--Massachusetts Institute of Technology, Dept. of Physics; and, (B.S.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1985.; Bibliography: leaf 141.
Tue, 01 Jan 1985 00:00:00 GMThttp://hdl.handle.net/1721.1/776771985-01-01T00:00:00ZAccelerated clustering through locality-sensitive hashinghttp://hdl.handle.net/1721.1/77534
Accelerated clustering through locality-sensitive hashing
Kishore, Shaunak
We obtain improved running times for two algorithms for clustering data: the expectation-maximization (EM) algorithm and Lloyd's algorithm. The EM algorithm is a heuristic for finding a mixture of k normal distributions in Rd that maximizes the probability of drawing n given data points. Lloyd's algorithm is a special case of this algorithm in which the covariance matrix of each normally-distributed component is required to be the identity. We consider versions of these algorithms where the number of mixture components is inferred by assuming a Dirichlet process as a generative model. The separation probability of this process, [alpha], is typically a small constant. We speed up each iteration of the EM algorithm from O(nd2k) to O(ndk log 3(k/a))+nd 2 ) time and each iteration of Lloyd's algorithm from O(ndk) to O(nd(k/a). 39) time.
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2012.; Cataloged from PDF version of thesis.; Includes bibliographical references (p. 18).
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/1721.1/775342012-01-01T00:00:00ZExperimental simulation of crevice corrosion of a functionally graded composite system of F91 and Fe-12Cr-2Si exposed to high-temperature lead-bismuth eutectic coolanthttp://hdl.handle.net/1721.1/76934
Experimental simulation of crevice corrosion of a functionally graded composite system of F91 and Fe-12Cr-2Si exposed to high-temperature lead-bismuth eutectic coolant
Ferry, Sara Elizabeth
In a system in which metal corrosion is of concern to its long-term structural integrity, crevice corrosion can be a significant cause of damage. Small crevices in a metal exposed to a working fluid (such as a reactor's coolant) may be prone to the development of a localized, aggressive reducing environment. If the metal relies on a passivating layer of oxides for corrosion protection, it may be vulnerable to corrosion attack within the crevice due to a drastically reduced oxygen potential and low pH. Furthermore, in a liquid metal environment, the reducing conditions combined with typically high solubilities of alloy components in the liquid metal can result in severe, localized crevice corrosion that surpasses that which might occur in the aqueous environment of a LWR. In this study, F91 and Fe-12Cr-2Si, two alloys used in previous experiments were exposed to lead-bismuth eutectic maintained at 715*C with a cover gas of pure hydrogen for thirty hours. The conditions were kept extremely reducing, via the initial removal of oxygen and the subsequent maintenance of an environment of pure hydrogen gas, in order to simulate conditions inside a crevice. Following the experiment, the materials were analyzed for corrosion damage via optical microscopy, scanning electron microscopy, and energy-dispersive x-ray spectroscopy. F91 was found to have sustained significant corrosion damage, as expected based on previous experiments, in addition to chromium depletion at the sample surface. Fe-12Cr-2Si was also found to have sustained corrosion damage as a result of lead-bismuth attack. No significant oxide formation or alloying element depletion was observed at the Fe-12Cr-2Si surface. The observed damage in Fe-12Cr-2Si was not entirely expected due to its excellent corrosion resistance in less reducing environments. This raises the concern that crevice corrosion could be an important damage mechanism in applications of the Fe-12Cr-2Si/F91 composite if crevices are present, either due to design flaws or due to cracking during service.
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2011.; "June 2011." Cataloged from PDF version of thesis.; Includes bibliographical references (p. 58-60).
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/1721.1/769342011-01-01T00:00:00Z